How To Get The Thinnest Lenses For Your Prescription

When buying new glasses, you probably want a pair with the thinnest lenses possible. Of course, if you have a medium or strong prescription you know that your lens will need to accommodate your prescription requirements. But don’t let the technical information puzzle you – we can quickly demystify the lens purchasing process to help you get the thinnest lenses for your frames!


When buying glasses, there are three primary factors that affect your overall lens thickness:
1. Your Prescription. Your prescription will ultimately determine how thick your lenses will be. The higher the prescription, the thicker the lens. 

In addition, prescriptions with astigmatism corrections often result in thicker lenses than those without astigmatism corrections. If your prescription has an astigmatism correction there will be values in the Cylinder (CYL) and Axis (sometimes abbreviated as X) fields.

2. Your Lens Index. The lens index refers to the lens’s “index of refraction,” which means how much the lens bends the light that enters it. This is important so that light is focused properly onto the retina, helping you see clearly when wearing your glasses.

In general, the higher the index, the thinner the lens. For example, a 1.61 lens is thinner than a 1.50 lens. You can change the index to thin the lens up to a certain point. After that point, the law of diminishing returns kicks in and altering your lens index further won’t thin your lenses or improve your vision. During the checkout process at Zenni, choosing a higher lens index will be the most direct way to ensure you have the thinnest lenses possible.

It is important to note that the lens index that is Recommended for your prescription when you are checking out will be the thinnest and most appropriate lens choice. We automatically suggest the best index choice based on your prescription and other information each time you buy a new pair of glasses. You might be thinking, “wow, can I just stop reading and check out?” While the answer is “yes,” we’ll explain further below so you can be confident in your purchase! (Note: prices listed are for clear lenses.)

3. Your Lens Size. The overall width and height of your lens can have considerable impact on the thickness of the lenses themselves. The bigger the lens, the thicker it tends to be. 

When buying frames at Zenni, the lens width and height are predetermined based on the frame you choose. Thus, aside from choosing frames based on factors like fashion or face shape, you should also shop based on size, as well as your eye doctor’s recommendations.

Now that you understand how your lens thickness is determined, let’s check out the lens index options at Zenni:

1.50 Standard Index

This is our most basic lens type (it’s free!) that is ideal for low prescriptions generally ranging from +1.00 to -2.00. If you have an extremely mild prescription, the standard index option will deliver the thinnest frame.

However, this lens index only features 85-90% UV protection in a clear lens. For 100% UV protection you will have to select a higher lens index, or a more advanced lens (such as a Blokz™ blue blocker lens).

1.57 Mid-Index

If you have a medium-level prescription, you’ll want this lens index in order to thin your lens. The 1.57 mid-index lens is the best option for farsighted prescriptions ranging from +2.00 to +1.00 and nearsighted prescriptions ranging from -3.00 to -2.00.

This lens also features 100% UV protection. Because we value our customers at Zenni, this lens is also free, so upgrade if you need to for your prescription, or if you want full UV protection (compared to a 1.50 lens).

1.53 Trivex Impact Resistant

This lens is ideal for prescriptions in both ranges above, but also delivers excellent impact resistance. Impact-resistant lenses are recommended for children’s glasses, sports glasses, as well as rimless and half-rim glasses.

1.53 Trivex lenses are the top choice for anyone who desires clear vision in an impact-resistant lens. Trivex is known for being crisp and clear, more scratch resistant, and 10% lighter than polycarbonate lenses. The improvement in visual clarity, reduction in scratches, and weight is worth the higher price of $29.95 compared to polycarbonate. This index will produce slightly thinner lenses when compared to those in a 1.50 standard index.

1.59 Polycarbonate Impact Resistant

1.59 Polycarbonate lenses also feature great impact resistance and, like Trivex, works best if your prescription falls between +2.00 and -4.00. If you have a stronger prescription, selecting a higher index will result in thinner lenses.

Polycarbonate lenses are significantly more affordable than Trivex, and are only moderately heavier. However, the clarity in polycarbonate lenses is slightly less than Trivex, and they tend to scratch more easily. In terms of thinness, this lens index is comparable to 1.53 Trivex impact- resistant, and thinner than 1.50 lenses. The price for 1.59 polycarbonate impact-resistant lenses is $9.

1.61 High Index

When you have a medium or strong prescription you need a higher index lens to keep your lenses thin. “High index” lenses come in indices of 1.61, 1.67, and 1.74. All three lenses are made with similar materials, so the choice of index comes down to your prescription strength. High-index lenses have good optical clarity, 100% UV protection, and excellent durability. Zenni is able to offer these lenses for incredible prices, whereas they can cost hundreds at traditional retailers.

A 1.61 high-index lens is best for farsighted prescriptions ranging between +3.00 and +2.00 and nearsighted prescriptions ranging from -6.00 to -4.00. It can even be a good choice for people with low prescriptions who want the additional lens benefits mentioned above. The price for 1.61 high-index lenses is $19.95.

1.67 High Index

Now we’re getting to indices for the really strong prescriptions. If you have a prescription ranging from +6.00 to +3.00 on the farsighted end or -10.00 to -6.00 on the nearsighted end, you’ll need one of our two strongest high index lenses. The 1.67 high index lens keeps your lenses fairly thin for an additional cost of $34.95.

1.74 High Index

When you have a really strong prescription, a 1.74 high-index lens will the thinnest option. Strong prescriptions in this range often fall within +12.00 to +6.00 and -10.00 to -26.00, but prescriptions in the 1.67 range may also benefit from some additional thinning in a 1.74 lens. The cost for this superior lens index is $74.95.

Playing With Lens Thickness

If you’d like to see how different lens types affect your lens thickness you can visit this third-party Lens Thickness Calculator and enter your prescription, PD, and lens size. Here you can see that increasing your lens index with a mild prescription won’t thin the lens, but when you have a strong prescription a higher lens index is needed.

If this seems like a lot of information, don’t worry – when you check out we automatically recommend the most appropriate lens index so you can leave the calculations to us! Start shopping today for your new favorite pair of shades or glasses.

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